Land Rover Repair: Air Compressor, air suspension, air compressor

Question
I have a 2000 Discovery II.  The air suspension on the drivers side rear sags from time to time.  When I got out of the vehicle the air compressor (we think) continued to run.  Only after disconnecting the battery did it turn off.  When you reconnect the battery it starts running again.  I drove it, thinking this would help, it didn't.

Answer
The sagging is most likely from leaks in the spring.  the can seal up depending on how much load or an un-even parking surface, so it will leak down randomly.

The compressor continuing to run is not right, possibly the relay failed closed, or a significant problem in the controll circuit.